JPH0473453B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to thermosetting reactive resin mixtures comprising polyfunctional epoxides, polyfunctional isocyanates and reaction promoters and optionally customary additives and/or fillers. [Prior art and its problems] In order to produce molding materials with high thermal and mechanical value, the electronic industry mainly uses acid anhydride-curable epoxide resins as impregnation and casting resins. . Conventional processing methods for epoxide resins, such as vacuum casting, VPI (vacuum pressure processing) and processing similar to injection molding, require resins that have a sufficient shelf life for the technical field. The minimum service life of epoxide resins is determined by various factors, such as post-treatment, casting time, casting volume and layer division, and can extend to several days. Significant advances in epoxide resins with regard to long service life have been achieved with the development of so-called latent reaction accelerators. With respect to the processing properties of epoxide resins, there are increasing demands on the hardness and also on the thermal and mechanical loadability of the molding materials produced therefrom. This fact particularly requires improved temperature change stability at the same time as high thermal shape stability. For epoxide resin molding materials cured with acid anhydrides, the upper limit for their thermal shape stability is approximately 150° C., if at the same time high mechanical properties and good temperature change stability are required. Reactive resin mixtures based on polyepoxides and polyisocyanates, so-called EP/IC resins, have therefore already been developed which, when thermally cured in the presence of suitable reaction accelerators, i.e. curing catalysts, exhibit thermal stability. This results in molding materials with oxazolidinone and isocyanurate structures, so-called OX/ICR molding materials. The thermal dimensional stability and permanent thermal stability of the reactive resin molding materials are increased by increasing the amount of isocyanurate structures, but at the same time the brittleness of the molding materials is increased and the temperature change stability is decreased. Object of the invention The object of the invention is to provide a thermosetting reactive resin mixture based on polyfunctional epoxides and polyfunctional isocyanates, which is storage stable and consists of well-mixable single components. , it is possible to produce molding materials which have a long service life during post-treatment and processing and at the same time the good mechanical properties and high temperature change stability of the polyurethane structure are combined with the good thermal properties of the OX/ICR structure. Our mission is to provide what we want. SUMMARY OF THE INVENTION This object, according to the invention, is such that the reaction resin mixture contains an isocyanate prepolymer as a polyfunctional isocyanate, a reaction product of diphenylmethane diisocyanate and a diol, or a reaction product of diphenylmethane diisocyanate and a functionality greater than 2. in the form of a reaction product of a diol with an isocyanate mixture consisting of polymethylene polyphenyl isocyanate having a polypropylene glycol, in each case containing 0.01 to 0.35 equivalents, preferably 0.05 to 0.2 equivalents, of diol per equivalent of isocyanate and 1 equivalent of epoxide. This is achieved by containing 0.2 to 5 equivalents of isocyanate per reaction and using a tertiary amine or imidazole as the reaction accelerator. The reactive resin mixtures according to the invention, which are preferably crosslinked and cured at temperatures from room temperature to 200° C., result in OX/ICR molding materials which also contain oxazolidinone and isocyanurate structures and, to a minor extent, urethane structures. These molding materials have outstanding mechanical properties and very good stability against temperature changes, at the same time as high thermal dimensional stability. The reactive resin mixtures according to the invention which contain isocyanate prepolymers in the form of reaction products of isocyanate compounds and diols have a long service life. Furthermore, the mixture consists of well-mixable individual components which are advantageous for processability. OX/ICR also has remarkable flexibility even when it contains a very small amount of isocyanate prepolymer resin mixture.
It was not expected that a molded material would form. When producing isocyanate prepolymers,
It is important to use from 0.01 to 0.35 equivalents of diol per equivalent of isocyanate (the isocyanate compound or mixture of isocyanates used). If the diol content of the reaction resin mixture is higher than this, the thermal dimensional stability of the molding material is clearly reduced, resulting in a molding material with properties that have already been realized industrially by other methods, and The viscosity of the seed reaction resin mixture is so high that it can no longer be processed with the addition of fillers. Attempts have already been made to combine the good mechanical properties of polyurethanes with the high thermal shape stability of OX/ICR molding materials by means of reactive resin mixtures consisting of epoxide resins, polyols and isocyanates (for this (see West German Patent Application No. 3001637). However, ternary systems of this type consisting of polyepoxide, polyol and polyisocyanate have definite drawbacks in terms of processing technology. This is because polyols and polyisocyanates undergo exothermic reactions to form urethanes even at low temperatures. This means a rapid increase in viscosity and unfavorable processability. This ternary system therefore cannot be used in many applications, especially for the impregnation of electrical windings. It is also well known that polyols and polyisocyanates often exhibit poor miscibility. Furthermore, the OH function acts cocatalytically in the trimerization of isocyanates (to isocyanurates) in the presence of amines, which are often used as curing catalysts, and thus supports crystallization. Furthermore, with the curable polymer mixtures according to DE 30 01 637 A1, the aim is to increase the thermal stability of known polyurethane molding materials to the level of anhydride-cured epoxide resin molding materials. . In this case, 0.7 to 1.4 equivalents of polyol are used per equivalent of isocyanate and 0.3 to 1 equivalent of epoxide are used per equivalent of isocyanate. In contrast, with the polyol-immiscible reactive resin mixture according to the invention, the OX/ICR molding material is mechanically improved, and its thermal shape stability far exceeds that of known anhydride-cured epoxide resin molding materials. Go around. A liquid epoxide compound containing at least two epoxide groups in the molecule with a polyisocyanate and optionally a polyhydroxyl compound,
A process for producing crosslinked polymers by reaction at temperatures from room temperature to 250° C. in the presence of a curing catalyst is known from DE 28 25 614 A1. However, this method uses exclusively acidic catalysts. i.e. the use of BF ₃ complex compounds with ethers, the use of phosphorus compounds or the use of water, optionally with Sn soluble in the reaction mixture described above as a curing catalyst,
It is necessary to use it together with Zn or Fe compounds. In the reaction resin mixture according to the invention epoxide 1
Contains 0.2 to 5 equivalents of isocyanate per equivalent. This means that the equivalent ratio of epoxide to isocyanate (EP:IC) is between 1:5 and 5:1. In the reactive resin mixture according to the invention, the polyisocyanate is present in the form of an isocyanate prepolymer. Compounds of this type are commercially available, but they can also be produced by known methods. For example, a liquid isocyanate prepolymer compound is known from German Patent Application No. 2737338, which comprises (a) 65 to 85% by weight of diphenylmethane diisocyanate and 15 to 85% by weight of polymethylene polyphenyl isocyanate with a functionality greater than 2. (b) an average molecular weight per equivalent of the isocyanate mixture;
200-600 polyexyethylene glycol
It consists of the reaction product with 0.0185 to 0.15 equivalents. However, this known isocyanate prepolymer, which is obtained exclusively by the reaction of isocyanate mixtures, is not used for EP/IC resins, but for the production of polyurethanes. Isocyanate prepolymers are also known from DE 25 13 793 A1. These polyisocyanates are prepared by adding 0.0005 to 0.35 equivalents of alkylene diol or polyoxyalkylene diol per equivalent of isocyanate group in the mixture, which is a mixture of polyphenyl polyisocyanates having methylene bridges containing 55 to 85% by weight of diphenylmethane diisocyanate. It is produced by reacting with In this case, preference is given to using 0.05 to 0.15 equivalents of alkylene diol, corresponding to a consumption of 5 to 15% of isocyanate groups. This polyisocyanate is also used in the production of polyurethane. A liquid, storage-stable isocyanate prepolymer is known from U.S. Pat. No. 3,394,164, which combines diphenylmethane diisocyanate with 2-10% by weight of dipropylene glycol and only a small amount (0.001-0.1% by weight, based on the isocyanate). It is produced by reaction in the presence of phosphoric acid at temperatures of 40-110°C. These prepolymers with a functionality of 2 and low viscosity are likewise used for the production of polyurethanes. When producing isocyanate prepolymers,
Low molecular weight monomeric diols such as ethylene glycol, propylene glycol and 1,6-hexanediol, and high molecular weight oligomeric diols such as polyoxyalkylene diols (which are produced by polymerizing alkylene oxides in the presence of water). can be used. Excellent compounds of this type are polyoxyethylene glycol and polyoxypropylene glycol. The reactive resin mixtures according to the invention advantageously contain isocyanate prepolymers in the form of reaction products of isocyanate mixtures of diphenylmethane diisocyanate and polymethylene polyphenyl isocyanate with alkylene diols or with polyoxyalkylene glycols. The polyoxyalkylene glycols used in this case advantageously have an average molecular weight of 100 to 1000, preferably 200 to 800. The polymethylene polyphenyl isocyanate content of the isocyanate mixture is preferably 35% by weight
That's it. The isocyanate prepolymers in the reaction resin mixture according to the invention can be used alone or in mixed form with other polyisocyanates. Relatively low-viscosity aliphatic, cycloaliphatic or aromatic isocyanates are particularly well suited as mixture components. In this case, isomer mixtures of 4,4'- and 2,4'-diphenylmethane diisocyanates and mixtures of liquid polyisocyanates and polymeric polyisocyanates or carbodiimide polyisocyanates are preferably used. It is a mixture. Other polyisocyanates that can be used are, for example, hexane-1,6-diisocyanate, cyclohexane-1,3-diisocyanate and its isomers,
4,4'-dicyclohexylmethane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate, 1,3
-dimethylbenzole ω,ω'-diisocyanate and its isomers, 1-methylbenzole-2,
4-diisocyanate and its isomers, naphthalene 1,4-diisocyanate, diphenyl ether-4,4'-diisocyanate and its isomers,
Diphenylsulfone-4,4'-diisocyanate and its isomers, as well as tri- or higher functional isocyanates such as 3,3',4,4'-diphenylmethanetetrisocyanate. Furthermore, it is also possible to use isocyanates masked with phenol or cresol in a conventional manner. Dimers and trimers of the polyvalent isocyanates mentioned above can be used as well. Polyisocyanates of this type have free isocyanate groups in the terminal positions and contain urethymine, uretedione and/or isocyanurate rings. Processes for the preparation of various types of trimers and uretediones of this type are described, for example, in U.S. Pat.
It is described in specifications No. 3494888, No. 3108100, and No. 2977370. Relatively low-viscosity aliphatic, cycloaliphatic or aromatic epoxides and mixtures thereof are particularly well suited as polyepoxides. Bisphenol-A-diglycidyl ether can be used advantageously,
bisphenol-F-diglycidyl ether,
3,4-epoxycyclohexylmethyl-3',
4′-epoxycyclohexane carboxylate,
Polyglycidyl ethers of phenol/formaldehyde or cresol/formaldehyde novolaks, diglycidyl esters of phthalic acid, isophthalic acid or terephthalic acid. Other polyepoxides that can be used are, for example, hydrogenated bisphenol-A- or bisphenol-F-
diglycidyl ether, hydantoin epoxide resin, triglycidyl isocyanurate, triglycidyl-p-aminophenol, tetraglycidyl diaminodiphenyl methane, tetraglycidyl diaminodiphenyl ether, tetrakis (4
-glycidoxyphenyl)-ethane, and “Handbook of Epoxy Resins” (Henry Lee
and Kris Neville, McGraw-Hill Book
Company, 1967) and Henry Lee's paper “Epoxy Resins” (American Chemical Society
1970). The reactive resin mixture according to the invention is further characterized by OX/
It may contain components that do not take part in the chemical reactions resulting in the ICR molding material. Fillers of this type include mineral and fibrous fillers, such as quartz powder, quartzite, aluminum oxide, glass powder, mica, kaolin, dolomite, graphite and carbon black, as well as carbon fibers, glass fibers and textile fibers. is suitable. Dyes, stabilizers and adhesives as well as other conventional additives can also be added to the reaction resin mixture. In the case of the EP/IC resin mixtures according to the invention, an important role is played by reaction accelerators or (curing) catalysts that aid the formation of OX and ICR rings during crosslinking. In this case, tertiary amines and imidazoles are used. Examples of tertiary amines include tetramethylethylenediamine, dimethyloctylamine, dimethylaminoethanol, dimethylbenzylamine, 2,4,6
-tris(dimethylaminomethyl)-phenol,
N,N'-tetramethyldiaminodiphenylmethane, N,N'-dimethylpiperazine, N-methylmorpholine, N-methylpiperidine, N-ethylpyrrolidine, 1,4-diazabicyclo(2,2,
2)-Octane and quinoline are suitable. Suitable imidazoles are, for example, 1-methylimidazole, 2-methylimidazole, 1,2-dimethylimidazole, 1,2,4,5-tetramethylimidazole, 2-ethyl-4-methylimidazole, 1-dianoethyl-2-phenyl enylimidazole and 1-(4,6-diamino-s-triazinyl-2-ethyl)-2-phenylimidazole. Furthermore, onium salts of tertiary amines and imidazoles, ie onium salts with N as the central atom, are suitable as reaction promoters for EP/IC resin mixtures. Examples of onium salts that can be used are tetraethylammonium chloride, tetraethylammonium bromide, octyltrimethylammonium bromide, benzyltrimethylammonium chloride, N-ethylmorpholinium bromide,
They are 2-ethyl-4-methylimidazolium bromide, N-ethylmorpholinium tetraphenylborate, 1,2-dimethylimidazolium tetraphenylborate, and tetrabutylammonium tetraphenylborate. The abovementioned catalysts result in thermally and mechanically expensive OX/ICR molding materials during the thermal curing of the EP/IC resins according to the invention, which is preferably carried out at temperatures from room temperature to 200.degree. These catalysts accelerate the curing reaction already at low temperatures and therefore do not in all cases provide an adequate service life and make the processing of the reaction resins difficult. However, the good miscibility of the starting components of the reaction resin mixture makes it possible to use these catalysts in all cases where processing is carried out according to the two-component principle and the mixing of the two components is carried out in static mixing tubes. I can do it. Therefore, in the EP/IC resin mixture according to the invention:
It is advantageous to use latent curing catalysts that guarantee a sufficient service life. Catalysts of this type, which are also characterized as latent reaction promoters, include in particular addition complexes of boron trihalides with tertiary amines and imidazole, such as boron trichloride and the general formula :BCI ₃・NR ¹
R ² R ³ (wherein R ¹ , R ² and R ³ are the same or different aliphatic, aromatic, heterocyclic or araliphatic groups,
Also, together they may be components of a heterocycle)
addition complexes with tertiary amines are suitable. formula:
Analogous complexes of boron trifluoride of BF ₃ .NR ¹ R ² R ³ in which R ¹ , R ² and R ³ are as defined above are also suitable. Excellent examples of suitable tertiary amines for BF ₃ and BCI ₃ complexes are octyldimethylamine and dimethylbenzylamine. Also morpholine compounds and imidazoles, especially N-methylmorpholine, N-ethylmorpholine, 1,2-dimethylimidazole and 1-benzyl-2-phenylimidazole.
Suitable in the form of BCI ₃ or BF ₃ complexes. The curing catalyst content in the EP/IC resin is preferably from 0.01 to 5% by weight, in particular from 0.25 to 2.5% by weight, based on the amount of resin matrix. In this case, the curing temperature and curing time are influenced by the type and concentration of the curing catalyst. The reactive resin mixtures according to the invention containing isocyanate prepolymers in the absence of catalysts give storage-stable mixtures which can be stored for several weeks without noticeable viscosity collapse and without precipitation of crystalline substances. can do. The use of latent curing accelerators also provides reactive resin systems with long service life and viscosity stability. These resin mixtures can also be processed by processes such as vacuum casting and VPI methods and processes similar to injection molding. Processing methods of this type are conventional for epoxides in the electronics industry. OX/ICR molding materials obtained after thermosetting from EP/IC resins containing isocyanate prepolymers are
It is characterized by high thermal dimensional stability as well as very good mechanical properties and good temperature change stability. This molding material is therefore suitable for impregnating and embedding electrical windings for rotating machines and transformers. The reactive resin mixtures according to the invention are also suitable for producing mechanically high-strength insulating devices, such as insulators, holding and supporting elements and bushings used in wiring and energy transmission technology. Other excellent applications are in the embedding and coating of electronic devices. [Examples of the Invention] The present invention will be described in detail below based on Examples. Examples 1 to 4 Bisphenol-F-bisglycidyl ether (BFBG, Ep value = 0.62 mol/100g, η ₅₀ °C =
1100 mPa s), a commercially available isocyanate prepolymer based on diphenylmethane diisocyanate and polypropylene glycol (Isocyanate A: NCO value = 0.59 mol/100 g, η ₂₅ °C
= 140 mPa・s), a liquid isomer mixture at room temperature of diphenylmethane diisocyanate (MDI;
NCO value = 0.79 mol/100g, η ₂₅ ℃ = 15mPa・s)
and 65% quartz powder (16900 H/cm ² ) and degassed for 1 hour at 80° C./1 mbar. Subsequently cool to 50°C and add a reaction accelerator (RKB), e.g.
BCl ₃・DMBA (BCl ₃ of dimethylbenzylamine
adduct) or CEPI (1-cyanoethyl-2-phenylimidazole) and degas for a further 1 hour at 50°C/1 mbar. The composition of the reaction resin mixture is shown in Table 1. The reaction resin mixture was heated to 100℃ in vacuo.
Pour into a preheated mold and heat at 140℃ for 4 hours and 200℃.
Cure for 16 hours at °C to form a molded mass. The molding material produced in this way meets DIN (German Industrial Standard) 53453.
Measure the impact strength (SZ) according to DIN53452, the bending strength (BF) according to DIN53452, and the thermal shape stability T _M according to Martens according to DIN53458. The values obtained are summarized in Table 2.

【table】

[Table] Examples 5 and 6 Bisphenol-F-bisglycidyl ether (BFBG, Ep value = 0.62 mol/100g, η ₅₀ °C =
1100 mPa·s), a commercially available isocyanate prepolymer based on diphenylmethane diisocyanate and polypropylene glycol (Isocyanate B: NCO value = 0.54 mol/100 g, η ₂₅ °C
= 650 mPa·s), together with a room temperature liquid isomer mixture of diphenylmethane diisocyanate (MDI) and 65% quartz powder, worked up as in Examples 1 to 4 and in the presence of a reaction accelerator (RKB). Processed into a molded substance. The composition of the reaction resin mixture appears from Table 3. Thermal and mechanical properties were measured on the cured molded materials in a manner analogous to that described in Examples 1-4. This is summarized in Table 4.

【table】

[Table] Examples 7 and 8 Bisphenol-F-bisglycidyl ether (BFBG, Ep value = 0.62 mol/100g, η ₅₀ °C =
1100 mPa・s), a commercially available isocyanate prepolymer based on polymethylene polyphenyl isocyanate and polypropylene glycol (Isocyanate C: NCO value = 0.63 mol/100 g,
η ₂₅ ℃ = 260 mPa・s), a liquid isomer mixture (MDI) of diphenylmethane diisocyanate at room temperature
and 65% quartz powder are worked up as in Examples 1 to 4 and processed into molding materials in the presence of a reaction accelerator (RKB). The composition of the reaction resin mixture is shown in Table 5. The thermal and mechanical properties were measured on the cured molding materials analogously to those described in Examples 1 to 4 and are summarized in Table 6.

【table】

[Table] Example 9 Bisphenol-F-bisglycidyl ether (BFBG, Ep value = 0.62 mol/100g, η ₅₀ ℃ =
1100 mPa s), a commercially available isocyanate prepolymer based on diphenylmethane diisocyanate and polypropylene glycol (Isocyanate A: NCO value = 0.59 mol/100 g, η ₂₅ °C
= 140mPa・s) and 65% dolomite (particle size: 98
%<63 .mu.m) and are worked up analogously to Examples 1 to 4 and processed into shaped materials in the presence of a reaction accelerator (RKB). The composition of the reaction resin mixture appears from Table 7. The thermal and mechanical properties were measured on the cured molding materials as described in Examples 1 to 4 and are summarized in Table 8.

【table】

[Table] Example ℃ mm ² mm ²

Claims (1)

[Scope of Claims] 1. A thermosetting reactive resin mixture containing a polyfunctional epoxide, a polyfunctional isocyanate, and a reaction accelerator, wherein the reactive resin mixture contains an isocyanate prepolymer as the polyfunctional isocyanate, diphenylmethane diisocyanate, and a diol. or a reaction product of a diol with an isocyanate mixture consisting of diphenylmethane diisocyanate and polymethylene polyphenyl isocyanate with a functionality greater than 2, in each case 0.01 diol per equivalent of isocyanate. -0.35 equivalents, 0.2 to 5 equivalents of isocyanate per equivalent of epoxide, and the reaction accelerator is a tertiary amine or imidazole. 2. Reactive resin mixture according to claim 1, characterized in that it contains customary additives and/or fillers. 3 Diol per equivalent of isocyanate
The reactive resin mixture according to claim 1 or 2, characterized in that it contains 0.05 to 0.2 equivalents. 4. Claims 1 to 4, characterized in that the reactive resin mixture contains an isocyanate prepolymer in the form of a reaction product of an isocyanate mixture consisting of diphenylmethane diisocyanate and polymethylene polyphenyl isocyanate and an alkylene diol. 4. Reactive resin mixture according to any one of clauses 3. 5. Claim 1, characterized in that the reactive resin mixture contains an isocyanate prepolymer in the form of a reaction product of a polyoxyalkylene glycol with an isocyanate mixture consisting of diphenylmethane diisocyanate and polymethylene polyphenyl isocyanate. 4. The reactive resin mixture according to any one of items 3 to 3. 6. The reactive resin mixture according to claim 5, wherein the polyoxyalkylene glycol has an average molecular weight of 100 to 1000. 7. The reactive resin mixture according to claim 6, wherein the polyoxyalkylene glycol has an average molecular weight of 200 to 800. 8. Reactive resin mixture according to any one of claims 1 to 7, characterized in that the isocyanate mixture contains up to 35% by weight of polymethylene polyphenyl isocyanate. 9. The reactive resin mixture according to any one of claims 1 to 8, characterized in that the reactive resin mixture contains a latent reaction accelerator. 10 Claims 1 to 9, characterized in that the reaction accelerator content is 0.01 to 5% by weight
Reactive resin mixture according to any one of clauses. 11. The reactive resin mixture according to claim 10, wherein the reaction accelerator content is 0.25 to 2.5% by weight. 12. Reactive resin mixture according to any one of claims 1 to 11, characterized in that the reactive resin mixture is crosslinked and cured at temperatures from room temperature to 200°C. 13 The reaction resin mixture contains quartz powder as a filler,
Claims 1 to 1, characterized in that they contain quartz, aluminum oxide, or dolomite.
3. Reactive resin mixture according to any one of 2.